The present application is a continuation application of PCT application No. PCT/JP01/10019 filed on Nov. 16, 2001. The present application claims priority from a Japanese Patent Application No. 2000-360067 filed on Nov. 27, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electron beam exposure apparatus for exposing a wafer by an electron beam. More particularly, it pertains to an electron beam exposure apparatus for generating a plurality of electron beams and exposing a wafer.
2. Description of the Related Art
A conventional electron beam generating apparatus includes an electron gun which includes a cathode for generating thermoelectrons, a grid for focusing the thermoelectrons generated by the cathode and for generating an electron beam, and an insulator for attaching the cathode and the grid, and a wafer is exposed by the electron beam generated by the single electron gun.
Recently, with expansion of demand of semiconductor devices, improvement in production rate of semiconductor devices is expected. However, since a wafer is exposed by single electron beam for generating the semiconductor devices in a conventional electron beam exposure apparatus, it is difficult to maintain sufficient production rate. Moreover, when it includes simply a plurality of above-mentioned electron guns to generate a plurality of electron beams, it is difficult to control the plurality of electron guns individually and it is also difficult to control electric discharge due to a number of thermoelectrons which are generated when the plurality of electron beams are generated.
In order to solve the aforesaid problem, according to the first aspect of the present invention, there is provided an electron beam generating apparatus for generating a plurality of electron beams. The electron beam generating apparatus includes: a plurality of cathodes for generating thermoelectrons; a cathode power supply unit for applying negative voltage to the cathodes so as to emit the thermoelectrons from the cathodes; a plurality of grids, which correspond to the plurality of cathodes respectively, for focusing the thermoelectrons emitted from each of the plurality of cathodes, and shaping the plurality of electron beams; and an insulator on which the plurality of cathodes and the plurality of grids are attached.
In the first aspect of the present invention, the cathode power supply unit may include a plurality of cathode power supplies, and each of the plurality of cathode power supplies may apply negative voltage to the plurality of cathodes. Moreover, the plurality of cathodes may be arranged in a gridiron pattern, and voltage may be applied to the plurality of cathodes, to which voltage is applied from one of the cathode power supplies, in accordance with a distance from a center of the gridiron pattern. Moreover, the electron beam generating apparatus may further include a first dummy electrode, which is positioned outside of outermost grids among the plurality of grids, on substantially the same surface as bottom surface of the insulator on which the plurality of grids are attached, and at substantially the same height as that of the outermost grids in a direction substantially perpendicular to the insulator.
The first dummy electrode may include a projection which projects from the surface, on which the plurality of grids are provided, to substantially opposite direction of the plurality of grids. Moreover the insulator may include: a high resistance film for covering at least a part of external surface of the insulator; a first electrode electrically connected to an upper part of the high resistance film; and a second electrode electrically connected to a lower part of the high resistance film. The second electrode may be electrically connected to one of the plurality of grids through the first dummy electrode, where substantially the same electric potential as the connected grid is applied, and substantially zero electric potential is applied to the second electrode. Moreover the electron beam generating apparatus may further include a second dummy electrode, which is positioned in a space insulated from the plurality of cathodes and the plurality of grids by the insulator, and electrically connected to the first dummy electrode. Moreover the second dummy electrode may be positioned so as to surround a connection unit which connects the cathode and the cathode power supply unit.
The plurality of grids may be arranged so that insulation resistance due to a clearance distance between one of the grids and another grid which adjoins the grid is lower than insulation resistance due to a creepage distance between one of the grids and another grid which adjoins the grid over surface of the insulator. Moreover, the electron beam generating apparatus may further include a plurality of cathode voltage fine adjustment units, which are positioned corresponding to the cathodes respectively, for adjusting voltage applied to each of the cathodes at higher resolution than that of the voltage generated by the cathode power supply. Moreover, the electron beam generating apparatus may further include a plurality of grid power supplies for applying voltage to each of the grids in accordance with electric potential of each of the cathodes which corresponds to each of the grids.
Moreover, the electron beam generating apparatus may further include a plurality of grid control units for controlling each of the plurality of grid power supplies so as to detect emission current which flows to each of the cathodes in accordance with an amount of the thermoelectrons generated by the plurality of cathodes, and to maintain each of the detected emission current to be substantially constant. Moreover the electron beam generating apparatus may further include: a plurality of filament current sources for supplying filament current for heating the cathodes to the plurality of cathodes respectively; a heating-current adjustment unit for adjusting current value of the filament current at each of the cathodes; and a heating-current control unit for controlling the current value of the filament current, which is adjusted by each of the heating-current adjustment units based on the current value of the plurality of electron beams which is to be shaped by the plurality of grids. Moreover the electron beam generating apparatus may further include a high tension cable including: a plurality of cathode cables for applying the filament current to each of the plurality of cathodes to which one of the cathode power supplies applies negative voltage; a plurality of grid cables for electrically connecting the plurality of grids and the plurality of grid power supplies, where each of the plurality of grids is corresponding to each of the plurality of cathodes to which one of the cathode power supplies applies negative voltage; an insulator for insulating the plurality of grid cables; and a shield which surrounds the insulator and of which electric potential is substantially the same as one of the plurality of cathodes.
Moreover, it is preferable that surface area of each of the cathodes is less than 3.5 square millimeters, and volume of each of the cathodes is more than 0.2 cubic millimeters. Moreover, the electron beam generating apparatus may further include a reflux unit for circulating insulating gas or insulating coolant to a space insulated from the plurality of cathodes and the plurality of grids by the insulator. Moreover the electron beam generating apparatus may further include a temperature control unit for controlling flow rate of the insulating gas or the insulating coolant in the reflux unit so as to maintain temperature of the insulator to be substantially constant.
According to the second aspect of the present invention, there is provided an electron beam exposure apparatus for exposing a wafer by an electron beam. The electron beam exposure apparatus includes: an electron beam generating apparatus for generating the electron beam; a deflector for deflecting the electron beam into a desired position on the wafer; and a stage for supporting the wafer. The electron beam generating apparatus includes: a plurality of cathodes for generating thermoelectrons; a cathode power supply unit for applying negative voltage to the cathodes so as to emit the thermoelectrons from the cathodes; a plurality of grids, which correspond to the plurality of cathodes respectively, for focusing the thermoelectrons emitted from each of the plurality of cathodes, and shaping the plurality of electron beams; and an insulator on which the plurality of cathodes and the plurality of grids are attached. The electron beam exposure apparatus may further include: a chamber for storing the electron beam generating apparatus, the deflector, and the stage; and a pressure reduction means for reducing a pressure of inside of the chamber. A vacuum area, of which the pressure is reduced by the pressure reduction means, in the chamber may be surrounded by a high resistance film or a conductor.
This summary of invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.